The formation of colour during biological treatment of pulp and paper wastewater

Colour discharges are gaining renewed focus in the pulp and paper industry as increasingly strict regulatory limits are placed on wastewater quality and aesthetics. In-mill process improvements, such as ECF bleaching and oxygen delignification, have decreased wastewater colour loadings. However, a survey of 12 pulp and paper mill systems found that effluent treatment using aerated stabilisation basins (ASB) leads to average increases in colour of 20-40%. In some instances, this phenomenon may even double the influent colour levels. Activated sludge systems did not produce a colour increase. The measured increases that follow ASB secondary treatment may be sufficient for a mill to fail prescribed discharge standards. A detailed field survey focusing on sections of an integrated bleached kraft mill ASB treatment system was undertaken. The average increase in colour at the final point of discharge was 45%. The major changes in colour concentration occurred in the inlet to the main treatment pond, and in polishing ponds that followed the main treatment pond. Both of these areas receive little or no aeration. No significant change was observed in the highly aerated main pond. These results, along with literature reports, suggested that redox conditions play a major role in influencing colour behaviour. To test this, two series of paired continuously stirred reactors were used to treat whole mill effluent from two ECF bleached kraft mills in parallel. The first series initially treated under anaerobic conditions, followed by an aerobic reactor, while the second series reversed this order. With the initial anaerobic stage, effluent colour increased by 18% and 19% for the first and second series respectively. Subsequent treatment by aerobic bacteria further increased colour by 14% and 6%, for a total increase of 32% and 25%. Initial aerobic treatment, however, did not lead to any significant change in colour for either effluent. Further anaerobic treatment following aerobic conditions produced only small increases in colour. These results are consistent with the ASB and activated sludge system survey, suggesting that anaerobic conditions at the head of treatment systems initiate the observed increases in effluent colour in ASB treatment systems.</jats:p

The limitations of draft assemblies for understanding prokaryotic adaptation and evolution

AbstractThe de novo assembly of next generation sequencing data is a daunting task made more difficult by the presence of genomic repeats or transposable elements, resulting in an increasing number of genomes designated as completed draft assemblies. We created and assembled idealized sequence data sets for Cupriavidus metallidurans CH34, Caulobacter sp. K31, Gramella forsetii KT0803, Rhodobacter sphaeroides 2.4.1 and Bordetella bronchiseptica RB50. In addition to confirming the role of transposable elements in interrupting the assemblies, an association was found between the most fragmented regions and known or predicted genomic islands in these strains. Assembly quality was more strongly related to putative genomic island content than to any other factor examined. We believe this association indicates that draft assemblies are limiting our ability to understand the genomic context of important bacterial adaptations and that the increased effort required for finishing genomes can provide a wealth of information for future studies

Comparison of tfdB sequences from bacterial isolates degrading 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol

Poster *INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA) Diffusion du document : INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA)International audienc

La diversité des gènes impliqués dans la dégradation de l'acide 2,4-dichlorophénoxyacétique illustre-t-elle une facilité de la microflore à s'adapter à de nouveaux substrats?

National audienc

Comparison of tfdB sequences from bacterial isolates degrading 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol

Poster *INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA) Diffusion du document : INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA)International audienc

The metabolic pathway of 2,4-dichlorophenoxyacetic acid degradation involves different families of tfdA and tfdB genes according to PCR-RFLP analysis

International audienceTwenty-five 2,4-dichlorophenoxyacetic acid (2,4-D) degrading bacteria from geographically diverse locations and presenting various degrees of similarity or no similarity to the tfdA and tfdB genes from Alcaligenes eutrophus JMP134 were analysed by PCR-RFLP (restriction length fragment polymorphism). Primers for the 2,4-D etherase gene were derived by sequence alignment of the tfdA genes from A. eutrophus JMP134 and Burkholderia sp. RASC. Primers for the 2,4-dichlorophenolhydroxylase gene were based on the tfdB gene sequence from A. eutrophus JMP134 by taking codon degeneration and variations in amino acid residue sequences into consideration. PCR amplification using the tfdA primer set produced fragments of 0.3 kb from 17 strains which showed varying degrees of similarity to the tfdA gene probe from A. eutrophus JMP134. Significant variations in the gene sequences were confirmed by PCR-RFLP analysis. DNA amplification using the tfdB primer set produced a 1.1 kb fragment from 19 strains. Amongst them, two did not show any similarity to the tfdB gene probe. The size and restriction pattern of the products obtained from A. eutrophus JMP134 were in accordance with the expected size calculated from the A. eutrophus tfdA and tfdB gene sequence and their theoretical PCR-RFLP patterns. Some strains which did not amplify using the tfdA primer set did however amplify with the tfdB primer set. These results suggest the independent evolution of these two genes in the construction of the 2,4-D metabolic pathway. Our tfdA and tfdB primer sets could be used for the detection of similar sequences in bacteria and soils. Moreover, PCR-RFLP patterns could also be used to select subsets of strains for sequencing to study the phylogeny of the tfdA and tfdB genes

La diversité des gènes impliqués dans la dégradation de l'acide 2,4-dichlorophénoxyacétique illustre-t-elle une facilité de la microflore à s'adapter à de nouveaux substrats?

*INRA Laboratoire de microbiologie des sols BP 86510 21065 Dijon cedex (FRA) Diffusion du document : INRA Laboratoire de microbiologie des sols BP 86510 21065 Dijon cedex (FRA)National audienc